1. Field of the Invention
This invention relates, for use with a fluid-providing device, to a dispensing chamber, and means for selectively transferring the fluid from its source to the chamber for drop dispensing, all without the necessity of pouring the fluid into a separate, disconnected container.
2. State of the Prior Art
The most common conventional method of providing blood serum for clinical analysis utilizes a plurality of containers in route to the actual test. That is, the blood sample is conventionally collected in an evacuated container, and separation of the serum from the whole cells may be achieved by centrifuging the sample within that container, or within another container to which the sample has been transferred. Thereafter, the serum is commonly poured off into yet another container for the desired clinical testing. All such transfer operations are time consuming, requiring either hand processing or complicated, expensive automatic handling. Furthermore, whenever there is a transfer of a liquid sample to a separate, open container, the sample is aerated and CO.sub.2 loss or gain can occur. Further, there is the danger of improper transfer, either by the use of the wrong container, by the improper patient labeling of the new container, or by both. There is also the danger of contamination by foreign materials, or infection of the operator. Devices which sequentially transfer a plurality of samples to the same dispensing device require careful cleaning of the dispensing device after each use. A system which keeps the blood sample confined to essentially the same container from its collection to the actual dispensing of serum for analysis is a distinct, sought-after improvement.
One evacuated container of the prior art which is particularly useful comprises a glass tube open only at one end, a septum fixed to that end when the tube is evacuated, and a movable plug contained within the tube. The plug is preferably a silica gel, with or without a cup-like mandrel positioned with its open end pointed to the septum. The container is spun about a centrifuge axis adjacent to the septum end, and the gel, by reason of its selected specific gravity, works up to the serum-cell interface where it plugs the container against remixing of the serum and cells. An example of such a container, but without the mandrel, is shown in U.S. Pat. No. 3,852,194.
Although such a device is useful in separating the serum from the cells, it has not avoided the transfer difficulties noted above.
Valving devices have been disclosed which are to be used with such evacuated containers described above, but the use is intended only in connection with the filling of such containers. U.S. Pat. No. 3,181,529 discloses such a device.
Still another approach to the problem of separating serum from whole blood involves the use of filters. The device disclosed in U.S. Pat. No. 3,687,296 is typical of such an approach.
There is disclosed in the commonly-owned application of R. Columbus, U.S. Ser. No. 548,670, filed on Jan. 30, 1975 entitled "Metering Apparatus", now abandoned in favor of a continuation-in-part application Ser. No. 644,014, filed Dec. 24, 1975, a recent innovation in devices for metering biological fluids such as blood serum. In that application, there is provided a cup-like container especially designed to dispense precise micro amounts of blood serum repeatedly. Each container is used for only one serum sample so that, among other things, sterilization problems are avoided. However, the serum for such metering is disclosed as being prepared from blood samples by conventional methods, requiring separate containers.
Early in medical history, aspirators were constructed comprising a fluid container, a piston movable within the container, a dispensing chamber in fluid communication with the container, and a valve selectively blocking flow from the container to the chamber. An example is shown in U.S. Pat. No. 657,440 issued Sept. 4, 1900. However, such devices were not designed for, and are not suitable as, a combination blood serum separation and dispensing device.
Patents relating only to the general background of blood separating devices in general, or valving means used in the collection of body fluids include the following U.S. Pat. Nos. 3,143,109; 3,308,809; 3,520,292; 3,661,265; 3,701,434; 3,750,645; 3,780,935 and 3,814,248.